Installed used transmission, now it slips in reverse? Bad tranny or install problem?

Hi,
I have a 1999 V6 Tacoma prerunner and I love my truck. A little over 300k miles the flywheel cracked and broke the torque converter and my transmission, so I bought a used transmission from a roll over truck that had 136k miles on it and had a local shop install it. It runs great, except today I tried to reverse up a steep incline and something went wrong. It will reverse at a low speed but when I press the gas to go faster It maintains the low speed and the engine revs up but it doesn't speed up passed a certain point. It made going up the hill difficult. I tried reversing on flat ground and the same thing happened when I tried to speed up. So, do you think the tranny is bad or not installed correctly? Any input is greatly appreciated!

 

There's not much in the install process that would cause this. Used parts are always a risk.

 

I take it this is a automatic transmission?

 

I would make sure correct amount of fluid is present. 1 qt low will make transmission slip.

 

Yes it is an automatic and it has enough fluid. Thanks

 

did they replace the fluid and filter in the tranny when they installed it? it could just be BLOCKED FILTER AFTER BEING ROLLED AND EVERYTHING STIRRED UP LIKE THAT.

damn cap lock keeps getting in the way, anyways

all sorts of crap could have been suspended to get into the filter but upside down and still running mare have burned some clutches in it too.

step one is drop the pan and check for debris or clogged filter, only after that will you be ready to ask the next question.

I have seen places take salvaged trannies and just bolt em in, period, nothing done but check the fluid level when its running.

also what year and model truck did the replacement tranny come from?